1. Field of the Invention
The present invention relates to an exposure apparatus and a method of manufacturing a device.
2. Description of the Related Art
A reduction projection exposure apparatus has been conventionally employed in a process of manufacturing a semiconductor element formed from an ultrafine pattern. This apparatus reduces and projects a circuit pattern drawn on a reticle (mask) onto a substrate such as a wafer coated with a photoresist, thereby exposing the substrate. Along with an improvement in packing density of semiconductor elements, it is demanded to further miniaturize circuit patterns. It is also demanded to realize an exposure apparatus which can uniform the finished pattern dimension (pattern line width).
A conventional exposure apparatus exposes a photoresist applied on a substrate with a dose appropriate to expose the photoresist. An exposure apparatus of the step & repeat scheme repeats exposure with a constant dose while moving across shot regions within the substrate plane. Unfortunately, even when the photoresist is repeatedly exposed with a constant dose in each shot within the substrate plane, a difference (pattern line width error) occurs between the line width of the obtained pattern and that of a design pattern. To maintain a given uniformity of the pattern line width, a variety of exposure methods of correcting the dose in accordance with each shot have been disclosed. One disclosed method controls the dose as an nth-degree polynomial function of the distance (position) from a predetermined position (origin) within the substrate plane to each shot.
Also, Japanese Patent Laid-Open No. 62-193125 proposes a technique of adjusting the slit width so as to reduce the unevenness of exposure attributed to a difference in illuminance in the non-scanning direction within the slit in an exposure apparatus of the step & scan scheme.
In the conventional techniques, although dose adjustment is often performed, it does not aim to uniform the line width distribution in a shot region. A conventional exposure apparatus which repeats exposures with a constant dose for respective shot regions cannot precisely reduce a pattern line width error in each shot region.